Do there exist sterile neutrino?

1. Since Pauli have postulated in 1933the existence of neutrino it remains one of the most interesting particles in nuclear physics J.Allen, 1957 Do thereexist sterile neutrino?

2. From history • W. Pauli proposed the existence of a neutral particle of low mass as “a desperate way out”. (1930 ) • E. Fermi renamed Pauli's particle as the "neutrino" and had incorporated the particle into a theory of β-decay. (1934) • Pauli: “I have invented something that cannot be detected” (It is obviously that he has underestimated ingenuities of the experimenters.) • F. Reines and C. Cowen detect ν from Savannah River reactor p(ν ,e+)n (1956) • W. Pauli proposed the existence of a neutral particle of low mass as “a desperate way out”. (1930 ) • E. Fermi renamed Pauli's particle as the "neutrino" and had incorporated the particle into a theory of β-decay. (1934) • Pauli: “I have invented something that cannot be detected” (It is obviously that he has underestimated ingenuities of the experimenters.) • F. Reines and C. Cowen detect ν from Savannah River reactor p(ν ,e+)n. (1956) Pontecorvo pioneers the thinking about oscillations, inspired by the neutral Kaon system: neutrino  antineutrino (1957). Idea was not generally accepted. Required large mixing of neutrinos and this went against accepted wisdom. Mikheyev and Smirnov develop theory or resonant oscillations. (1987) Solar neutrino experiments proved neutrino oscillations. (2001)

3. Now (1967) Pontecorvo coins the wording “sterile neutrino” (1990 - ) Research of the neutrino oscillation is started. For the interpretation of sets of obtained results were demanded sterile neutrinos. The theory intensively tries to build now a new physics beyond the standard model for accommodationsterile neutrinos.

4. • If accept sterile neutrino hints, then should be checked and quantified neutrino oscillations in all channels: – νe andνe appearance – νμ andνμ disappearance – νe andνe disappearance But in experiments the inconsistent results are received New experiments are very needed

5. Hints for High Δm2~1 eV2 Oscillation ⇒ Sterile Neutrinos? or Something Else? • Positive indications: – LSND/MiniBooNEνμ→νe appearance signal – MiniBooNE low-energy excess (νμ→νe ?) – Reactor disappearance anomaly (νe→νe ) – Gallex-Sage reduced calibration source rate (νe disappearance?) • Negative indications: – CDHS and MiniBooNE restrictions on νμ disappearance – MiniBooNE restrictions onνμ disappearance – Karmen restrictions on νμ→νe – Other negative results

6. The cross sections for neutrino capture to the two lowest excited states in 71Ge have been overestimated (W. Haxton) Maximum contribution of these excited states – 5%. If the contribution of these states to the predicted rate were to be zero then R = 0.92 ± 0.06 and the fit to the expected value of 1.0 becomes quite reasonable (χ2 /dof = 4.58/3, GOF =21%). The measurements of (3He, t) reaction on Ga cross section were carried out in RCNP (Research Center for Nuclear Physics), Japan (H. Ejiri) last year. “ At RCNP we recently re-measured the GT transition strengths to various states in 71Ge with the main objective to extract the GT strength values to the g.s., the 175 keV and the 500 keV states with highest resolution and highest possible accuracy using the (3He,t) reaction at 420 MeV and the Grand Raiden spectrometer. …. one arrives at a value of6.9 ± 1.8% for the contribution from the excited states in 71Ge to the neutrino capture cross section.This is a slightly larger value than the one, which was roughly estimated by Bahcall and therefore slightly amplifies the discrepancy observed in the calibration measurements.” “… it may be worthwhile to review past measurements of the 71Ge EC Q-value and lifetime, which together define the final ft-value.” [TRIUMF Research Proposal]

7. TRIUMF Research Proposal Q-value measurement for the 71Ge electron capture Spokespersons : D. Frekers, J. Dilling, H. Ejiri We propose to measure the electron capture Q-value of 71Ge leading to the ground state of 71Ga using the TITAN(TRIUMF's Ion Trap for Atomic and Nuclear science) ion trap mass measurement facility. The exact mass difference is an important quantity, which enters into the neutrino cross section on 71Ga, and which needs to be known with high precision. 71Ga was the material, which was used in the solar neutrino experiments SAGE and GALLEX and subsequently for the detector calibration with neutrinos from a 51Cr calibration source. A renewed mass measurement using the ion trap technique will help to clarify the origin of a rather long-standing and still unresolved discrepancy of the calibration measurements performedby both neutrino experiments, SAGE and GALLEX. The TITAN Beamline

8. Vote for the Ga- BOREXINO source experiment!